Workaround for 'Inherit Rotation' in armature?
I can't tell you how to solve your problem but I think I can tell you about the helper bone.

Long time ago I implemented a bvh importer for another software (not blender), to get it working with the rotations given in the bvh file I had to add an helper bone for each existing bone.

A zero length bone (no influence to the mesh) placed at the origin of the original bone, and obviously the original bone must be parented with the helper (original child, helper parent), all the rotations are applied to the helper only.